/*
 * 版权：河南魔丸科技有限公司 版权所有
 * @author Zhaimm
 * 创建日期：2020/10/8 3:25 PM
 * 文件名：ZMTabIndicator
 */

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// @dart = 2.8

import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';


/// Used with [TabBar.indicator] to draw a horizontal line below the
/// selected tab.
///
/// The selected tab underline is inset from the tab's boundary by [insets].
/// The [borderSide] defines the line's color and weight.
///
/// The [TabBar.indicatorSize] property can be used to define the indicator's
/// bounds in terms of its (centered) widget with [TabBarIndicatorSize.label],
/// or the entire tab with [TabBarIndicatorSize.tab].
class ZMTabIndicator extends Decoration {
  /// Create an underline style selected tab indicator.
  ///
  /// The [borderSide] and [insets] arguments must not be null.
  const ZMTabIndicator({
    this.borderSide = const BorderSide(width: 2.0, color: Colors.white),
    this.insets = EdgeInsets.zero,
  }) : assert(borderSide != null),
        assert(insets != null);
  
  /// The color and weight of the horizontal line drawn below the selected tab.
  final BorderSide borderSide;
  
  /// Locates the selected tab's underline relative to the tab's boundary.
  ///
  /// The [TabBar.indicatorSize] property can be used to define the tab
  /// indicator's bounds in terms of its (centered) tab widget with
  /// [TabBarIndicatorSize.label], or the entire tab with
  /// [TabBarIndicatorSize.tab].
  final EdgeInsetsGeometry insets;
  
  @override
  Decoration lerpFrom(Decoration a, double t) {
    if (a is ZMTabIndicator) {
      return ZMTabIndicator(
        borderSide: BorderSide.lerp(a.borderSide, borderSide, t),
        insets: EdgeInsetsGeometry.lerp(a.insets, insets, t),
      );
    }
    return super.lerpFrom(a, t);
  }
  
  @override
  Decoration lerpTo(Decoration b, double t) {
    if (b is ZMTabIndicator) {
      return ZMTabIndicator(
        borderSide: BorderSide.lerp(borderSide, b.borderSide, t),
        insets: EdgeInsetsGeometry.lerp(insets, b.insets, t),
      );
    }
    return super.lerpTo(b, t);
  }
  
  @override
  _ZMPainter createBoxPainter([ VoidCallback onChanged ]) {
    return _ZMPainter(this, onChanged);
  }
  
  Rect _indicatorRectFor(Rect rect, TextDirection textDirection) {
    assert(rect != null);
    assert(textDirection != null);
    final Rect indicator = insets.resolve(textDirection).deflateRect(rect);
    //希望的宽度
    double wantWidth = 20;
    //取中间坐标
    double cw = (indicator.left + indicator.right) / 2;
    return Rect.fromLTWH(
      cw - wantWidth / 2,
      indicator.bottom - borderSide.width,
      wantWidth,
      borderSide.width,
    );
    
    // return Rect.fromLTWH(
    //   indicator.left ,
    //   indicator.bottom - borderSide.width,
    //   indicator.width,
    //   borderSide.width,
    // );
  }
  
  @override
  Path getClipPath(Rect rect, TextDirection textDirection) {
    return Path()..addRect(_indicatorRectFor(rect, textDirection));
  }
}

class _ZMPainter extends BoxPainter {
  _ZMPainter(this.decoration, VoidCallback onChanged)
      : assert(decoration != null),
        super(onChanged);
  
  final ZMTabIndicator decoration;
  
  @override
  void paint(Canvas canvas, Offset offset, ImageConfiguration configuration) {
    assert(configuration != null);
    assert(configuration.size != null);
    final Rect rect = offset & configuration.size;
    final TextDirection textDirection = configuration.textDirection;
    final Rect indicator = decoration._indicatorRectFor(rect, textDirection).deflate(decoration.borderSide.width / 2.0);
    final Paint paint = decoration.borderSide.toPaint()..strokeCap = StrokeCap.round;
    canvas.drawLine(indicator.bottomLeft, indicator.bottomRight, paint);
  }
}
